Geoscience Reference
In-Depth Information
6. Large-scale tests of ground rupture effects on HDPE pipelines
A third series of experiments is being performed as part of joint research supported by
the National Science Foundation (NSF) through the George E. Brown, Jr., Network for
Earthquake Engineering Simulation (NEES), using the large-scale lifeline testing facil-
ity at Cornell University and the 150g-ton centrifuge at Rensselaer Polytechnic Institute
(RPI). Information about the experimental program is provided by Cornell et al. (2006).
Due to space limitations, only the salient features of the large-scale experiments are pro-
vided herein.
The soil for the large-scale experiments on HDPE is a glacio-fluvial, well graded
sand similar to that used for full-scale experiments of soil-pipeline interaction on steel
pipelines with elbows that were described previously (see Figure 17.13). The sand was
placed and compacted in 200-mm-thick lifts. Moisture content was determined using a
nucleardensitygageaswellassoilsamplesremovedinstandardtinsformoisturecontent
determinationinthelaboratory.Fortymoisturecontentand40soildensitymeasurements
weretakenperlift,foratotalof320measurementsover8lifts.Themeandryunitweight
for all soil placed was 15
32kN m
−
3
. There
is 95% confidence that the mean dry unit weight of soil placed for testing is between
15
7kNm
−
3
, with a standard deviation of 0
.
.
72kN m
−
3
. Based on direct shear calibrations, the peak soil fric-
tionangleisbetween39
◦
and40
◦
.Meanmoisturecontentwas4.1%,withastandarddevi-
ation of 0.77%. The 95% confidence interval for the mean moisture content is between
4.05% and 4.20%.
66kN m
−
3
and 15
.
.
The experimental plastic pipelines were nominal 400-mm-diameter and nominal 250-
mm-diameter, IPS, HDPE pipes, manufactured by the Chevron Phillips Chemical Com-
panyunderthecommercialnameDRISCOPLEX.Thenominal400-mmpipehasanout-
sidediameterof400.5mmandwallthickness24mm.Electrofusion(EF)couplingswere
installed at each end of each specimen to provide anchor locations for connecting the
experimental pipeline to the split-box test basin. The couplings use computer-controlled
heating coils to fuse, or thermally bond, onto the HDPE pipe so that they are connected
to the pipe at a strength comparable with that of the HDPE. The instrumentation layout
forthetestonthe400-mm-diameterpipelineincluded148straingages,andwasplanned
using results from finite element (FE) analyses. The experimental pipeline was buried at
a depth of 0.9mfromground surface to top of pipe.
Figure 17.18 shows an overhead view of the large-scale ground rupture test on the
400-mm-diameter HDPE pipeline. The split-box experimental chamber was approxi-
mately 10.7m long, 3.2m wide, and filled to a total depth of 1.5m with partially sat-
urated sand. The test involved approximately 91 metric tons of sand. A left lateral strike
slip displacement of 1.2m was imposed during testing over a period of 4min. The angle
of intersection between the rupture plane and pipeline was 65
◦
, which induced tension
and bending inthepipe.
Only the central 6m of the experimental chamber are shown. The deformed shape of
the pipeline is superimposed on the photo. The deformed shape was measured with
